Move checkpoint creation to under the strategy scope. This bug was crashing TPU examples in the case of preemption.
Move checkpoint creation to under the strategy scope. This bug was crashing TPU examples in the case of preemption.

PiperOrigin-RevId: 345595930
Change-Id: Ie78cfe5510a54a23aa8af85bc87476a97b63dccc

tensorflow/agents,tensorflow/agents